| From 24bc3928aa543d9a13c822733d3a23faf47ad43f Mon Sep 17 00:00:00 2001 |
| From: Michal Hocko <mhocko@suse.com> |
| Date: Wed, 20 Feb 2019 22:20:46 -0800 |
| Subject: mm, memory_hotplug: fix off-by-one in is_pageblock_removable |
| |
| [ Upstream commit 891cb2a72d821f930a39d5900cb7a3aa752c1d5b ] |
| |
| Rong Chen has reported the following boot crash: |
| |
| PGD 0 P4D 0 |
| Oops: 0000 [#1] PREEMPT SMP PTI |
| CPU: 1 PID: 239 Comm: udevd Not tainted 5.0.0-rc4-00149-gefad4e4 #1 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 |
| RIP: 0010:page_mapping+0x12/0x80 |
| Code: 5d c3 48 89 df e8 0e ad 02 00 85 c0 75 da 89 e8 5b 5d c3 0f 1f 44 00 00 53 48 89 fb 48 8b 43 08 48 8d 50 ff a8 01 48 0f 45 da <48> 8b 53 08 48 8d 42 ff 83 e2 01 48 0f 44 c3 48 83 38 ff 74 2f 48 |
| RSP: 0018:ffff88801fa87cd8 EFLAGS: 00010202 |
| RAX: ffffffffffffffff RBX: fffffffffffffffe RCX: 000000000000000a |
| RDX: fffffffffffffffe RSI: ffffffff820b9a20 RDI: ffff88801e5c0000 |
| RBP: 6db6db6db6db6db7 R08: ffff88801e8bb000 R09: 0000000001b64d13 |
| R10: ffff88801fa87cf8 R11: 0000000000000001 R12: ffff88801e640000 |
| R13: ffffffff820b9a20 R14: ffff88801f145258 R15: 0000000000000001 |
| FS: 00007fb2079817c0(0000) GS:ffff88801dd00000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 0000000000000006 CR3: 000000001fa82000 CR4: 00000000000006a0 |
| Call Trace: |
| __dump_page+0x14/0x2c0 |
| is_mem_section_removable+0x24c/0x2c0 |
| removable_show+0x87/0xa0 |
| dev_attr_show+0x25/0x60 |
| sysfs_kf_seq_show+0xba/0x110 |
| seq_read+0x196/0x3f0 |
| __vfs_read+0x34/0x180 |
| vfs_read+0xa0/0x150 |
| ksys_read+0x44/0xb0 |
| do_syscall_64+0x5e/0x4a0 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| and bisected it down to commit efad4e475c31 ("mm, memory_hotplug: |
| is_mem_section_removable do not pass the end of a zone"). |
| |
| The reason for the crash is that the mapping is garbage for poisoned |
| (uninitialized) page. This shouldn't happen as all pages in the zone's |
| boundary should be initialized. |
| |
| Later debugging revealed that the actual problem is an off-by-one when |
| evaluating the end_page. 'start_pfn + nr_pages' resp 'zone_end_pfn' |
| refers to a pfn after the range and as such it might belong to a |
| differen memory section. |
| |
| This along with CONFIG_SPARSEMEM then makes the loop condition |
| completely bogus because a pointer arithmetic doesn't work for pages |
| from two different sections in that memory model. |
| |
| Fix the issue by reworking is_pageblock_removable to be pfn based and |
| only use struct page where necessary. This makes the code slightly |
| easier to follow and we will remove the problematic pointer arithmetic |
| completely. |
| |
| Link: http://lkml.kernel.org/r/20190218181544.14616-1-mhocko@kernel.org |
| Fixes: efad4e475c31 ("mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone") |
| Signed-off-by: Michal Hocko <mhocko@suse.com> |
| Reported-by: <rong.a.chen@intel.com> |
| Tested-by: <rong.a.chen@intel.com> |
| Acked-by: Mike Rapoport <rppt@linux.ibm.com> |
| Reviewed-by: Oscar Salvador <osalvador@suse.de> |
| Cc: Matthew Wilcox <willy@infradead.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| mm/memory_hotplug.c | 27 +++++++++++++++------------ |
| 1 file changed, 15 insertions(+), 12 deletions(-) |
| |
| diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c |
| index ff93a57e1694..156991edec2a 100644 |
| --- a/mm/memory_hotplug.c |
| +++ b/mm/memory_hotplug.c |
| @@ -1213,11 +1213,13 @@ static inline int pageblock_free(struct page *page) |
| return PageBuddy(page) && page_order(page) >= pageblock_order; |
| } |
| |
| -/* Return the start of the next active pageblock after a given page */ |
| -static struct page *next_active_pageblock(struct page *page) |
| +/* Return the pfn of the start of the next active pageblock after a given pfn */ |
| +static unsigned long next_active_pageblock(unsigned long pfn) |
| { |
| + struct page *page = pfn_to_page(pfn); |
| + |
| /* Ensure the starting page is pageblock-aligned */ |
| - BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); |
| + BUG_ON(pfn & (pageblock_nr_pages - 1)); |
| |
| /* If the entire pageblock is free, move to the end of free page */ |
| if (pageblock_free(page)) { |
| @@ -1225,16 +1227,16 @@ static struct page *next_active_pageblock(struct page *page) |
| /* be careful. we don't have locks, page_order can be changed.*/ |
| order = page_order(page); |
| if ((order < MAX_ORDER) && (order >= pageblock_order)) |
| - return page + (1 << order); |
| + return pfn + (1 << order); |
| } |
| |
| - return page + pageblock_nr_pages; |
| + return pfn + pageblock_nr_pages; |
| } |
| |
| -static bool is_pageblock_removable_nolock(struct page *page) |
| +static bool is_pageblock_removable_nolock(unsigned long pfn) |
| { |
| + struct page *page = pfn_to_page(pfn); |
| struct zone *zone; |
| - unsigned long pfn; |
| |
| /* |
| * We have to be careful here because we are iterating over memory |
| @@ -1257,13 +1259,14 @@ static bool is_pageblock_removable_nolock(struct page *page) |
| /* Checks if this range of memory is likely to be hot-removable. */ |
| bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) |
| { |
| - struct page *page = pfn_to_page(start_pfn); |
| - unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page))); |
| - struct page *end_page = pfn_to_page(end_pfn); |
| + unsigned long end_pfn, pfn; |
| + |
| + end_pfn = min(start_pfn + nr_pages, |
| + zone_end_pfn(page_zone(pfn_to_page(start_pfn)))); |
| |
| /* Check the starting page of each pageblock within the range */ |
| - for (; page < end_page; page = next_active_pageblock(page)) { |
| - if (!is_pageblock_removable_nolock(page)) |
| + for (pfn = start_pfn; pfn < end_pfn; pfn = next_active_pageblock(pfn)) { |
| + if (!is_pageblock_removable_nolock(pfn)) |
| return false; |
| cond_resched(); |
| } |
| -- |
| 2.19.1 |
| |